The invention relates to a separator for separating oil mist from the crankcase ventilation gas of an internal combustion engine, especially of a motor vehicle; with a gas purification chamber inside which a rotatably mounted centrifugal rotor is arranged. The gas purification chamber has a crude gas inlet, a pure gas outlet, and an oil outlet. The crankcase ventilation gas can be conducted into a radially internal zone of the centrifugal rotor via the crude gas inlet, while pure gas liberated from oil mist can be discharged from the gas purification chamber via the pure gas outlet, and oil separated from the gas can be discharged from the gas purification chamber via the oil outlet. The separator comprises a rotary drive for the centrifugal rotor, the rotary drive being arranged in a drive chamber of the separator, the drive chamber being separately arranged from the gas purification chamber, and the drive can be operated using pressurized lubrication oil of the internal combustion engine and is connected to the centrifugal rotor by means of a shaft extending from the drive chamber into the gas purification chamber. The rotary drive is formed by at least one thrust nozzle which is connected to the shaft and to which the pressurized lubrication oil of the internal combustion engine can be fed. The invention furthermore relates to a functional module and an internal combustion engine which are provided with a corresponding separator.
A first separator is known from WO 2004/091 799 A. In this known separator, the rotary drive is formed by an impeller wheel arranged on the shaft onto which pressurized lubrication oil of the internal combustion engine can be sprayed through at least one stationary installed nozzle. It is considered disadvantageous with this known separator that its rotary drive has a relatively bad efficiency so that a large volume of pressurized lubrication oil is consumed to achieve the desired high speed of the centrifugal rotor, said oil then being no longer available for the lubrication of the associated internal combustion engine. It is accordingly required in many cases to provide a higher output oil pump or an additional oil pump for the rotary drive of the separator which results in increased manufacturing costs. If the last-named measures increasing the costs are avoided, the disadvantage is to be accepted that the achievable maximum speed of the centrifugal rotor is limited, due to which the separating performance of the separator also remains limited, and accordingly the task conceived for the separator is not reliably fulfilled, namely de-oiling the crankcase ventilation gas to the farthest extent possible.
Another separator is known from U.S. Pat. No. 6,709,477 B1. With this additionally known separator as well, an impeller wheel arranged on the shaft is provided as rotary drive for the centrifugal rotor and a liquid jet is sprayed onto it, usually pressurized lubrication oil of an associated internal combustion engine. This separator has the same disadvantages as the above described first known separator.
A lubrication oil centrifuge is known from WO 1999/056 883 A for cleaning the lubrication oil of an internal combustion engine, with a separator for separating oil from the crankcase ventilation gas being set onto a rotor of the centrifuge, and the separator can be set to rotate together with the rotor of the centrifuge. The lubrication oil centrifuge is driven by thrust nozzles through which the lubrication oil centrifuged in the rotor of the centrifuge exits into a pressureless chamber surrounding the centrifuge. From this chamber, the lubrication oil flows off, without pressure, through a channel of a correspondingly large cross-section and preferably back into the oil pan of the associated internal combustion engine. The separator set onto the rotor of the centrifuge is here used for de-oiling the crankcase ventilation gas. The crankcase ventilation gas to be liberated from oil mist flows in counterflow to the flowing-off lubrication oil through its return flow channel into the chamber in which the lubrication oil exits from the thrust nozzles. The crankcase ventilation gas flows through this chamber upwardly to the separator above the rotor and arranged on is to be considered disadvantageous in this device that the crankcase ventilation gas is passed through the return flow channel for the lubrication oil and through the chamber in which the lubrication oil exits from the thrust nozzles; and the crankcase ventilation gas is accordingly burdened with a considerable additional oil load which the crankcase ventilation gas entrains on its further way to the separator. An unnecessarily large amount of oil mist or oil droplets must therefore be separated from the crankcase ventilation gas in the separator. As a consequence, the separator must be relatively large in design and thus occupy a large structural space to ensure the necessary separation; or oil portions remain in the crankcase ventilation gas after its passage through the separator. Both specified consequences are undesirable since the aim is always the smallest possible structural space and the highest possible degree of separation. Moreover, the maximum achievable speed of a lubrication oil centrifuge is too low for good oil mist separation which results in a bad efficiency of a separator combined with a lubrication oil centrifuge.
A separator of the initially indicated type is known from WO 2007/073 320 A. The rotor of this separator is preferably rotatably provided in its own frame which can be set into a housing and fixed therein. This document does not provide any further concrete information regarding the execution of the bearing; however, the presentations of the exemplary embodiment in the drawing FIGS. 2 and 4 show that two bearings of the shaft of the rotor lie relatively closely together in axial direction and that the assembly of the multipart frame in the area of the bearings is complex since several screws are required. This construction moreover shows that the bearing of the rotor is not particularly favorable in design and that particularly desirable high speeds of the rotor are not achievable.